• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.287-297
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• 2018

To improve the performance of sensorless induction motor (IM) drives, a novel speed estimation method based on the real-time adaptive extended Kalman filter (RAEKF) is proposed in this paper. In this algorithm, the fuzzy factor is introduced to tune the measurement covariance matrix online by the degree of mismatch between the actual innovation and the theoretical. Simultaneously, the fuzzy factor can be continuously self-tuned tuned by the fuzzy logic reasoning system based on Takagi-Sugeno (T-S) model. Therefore, the proposed method improves the model adaptability to the actual systems and the environmental variations, and reduces the speed estimation error. Furthermore, a simple exponential function based on the fuzzy theory is used to reduce the computational burden, and the real-time performance of the system is improved. The correctness and the effectiveness of the proposed method are verified by the simulation and experimental results.

• Economic and Environmental Geology
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• v.33 no.1
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• pp.61-75
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• 2000

Through modeling fault network using thin plate finite element technique in the San Andreas Fault system with slip rate over 1mm/year, as well as elevation, heat flow, earthquakes, geodetic data and crustal thickness, we compare the results with velocity boundary conditions of plate based on the NUVEL-1 plate model and the approximation of deformation in the Great Basin region. The frictional and dislocation creep constants of the crust are calculated to reproduce the observed variations in the maximum depth of seismicity which corresponds to the temperature ranging from $350^{\circ}C$ to $410^{\circ}C$. The rheologic constants are defined by the coefficient of friction on faults, and the apparent activation energy for creep in the lower crust. Two parameters above represent systematic variations in three experiments. The pattern of model indicates that the friction coefficient of major faults is 0.17~0.25. we test whether the weakness of faults is uniform or proportional to net slip. The geologic data show a good agreement when fault weakness is a trend of an additional 30% slip dependent weakening of the San Andreas. The results of study suggest that all weakening is slip dependent. The best models can be explained by the available data with RMS mismatch of as little as 3mm/year, so their predictions can be closely related with seismic hazard estimation, at least along faults where no data are available.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.134-139
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• 2007

This paper presents a computer-based analysis on the thermal shock characteristics of Pb-free solder joints and UBM in flip chip assemblies. Among four types of popular UBM systems, TiW/Cu system with 95.5Sn-3.9Ag-0.6Cu solder joints was chosen for simulation. A simple 3D finite element model was first created only including silicon die, mixture between underfill and solder joints, and substrate. The displacements due to CTE mismatch between silicon die and substrate was then obtained through FE analysis. Finally, the obtained displacements were applied as mechanical loads to the whole 2D FE model and the characteristics of flip chip assemblies were analyzed. In addition, based on the hyperbolic sine law, the accumulated creep strain of Pb-free solder joints was calculated to predict the fatigue life of flip chip assemblies under thermal shock environments. The proposed method for fatigue life prediction will be evaluated through the cross check of the test results in the future work.

• Korean System Dynamics Review
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• v.11 no.4
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• pp.117-142
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• 2010

National territorial policies require a series of dynamic simulations, which would facilitate effectiveness measuring and forecasting works geared towards territorial policies under consideration or implementation. This paper aims at designing an integrated prototype for the proposed territorial policies. After the simulation exercises for the Ochang Industrial Complex(OIC) in Chungbuk Province, this study firstly finds meaningful mismatch phenomena between housing and population increases as the in-migration time lag seems inevitable even after the housing construction is in a mature state. Secondly, the OIC development exerts more significant impact on the number of employees than that of business units. Thirdly, in- and out-migration orders are different during the first and second stages of OIC development. That is, Chungbuk Province records the largest in terms of in-migration volume, followed by the Capital and Non-Capital Regions. Even though Chungbuk Province ranks the top position in the out-migration volume, the rank of the Capital and Non-Capital Regions is reversed: the our-migration volume towards the Non-Capital Region outruns that of the Capital Region.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.55-62
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• 2004

Even though FOPDT(First-Order Plus Dead-Time) process is most widely applied in the industrial control field, it is difficult to figure out a in precise process model because of the long dead-time problem. Also, control performance may be deteriorated due to the mismatch problem of plant and model. Thus, the accuracy of process identification is the most important problem in FOPDT process control. In this paper, the proposed method using real-coded genetic algorithm outperforms the existing estimation methods that use step-test responses. The proposed strategy obtained useful result through a number of simulation examples.

• ETRI Journal
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• v.31 no.5
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• pp.619-621
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• 2009

In this letter, we study the influence of receiver imperfections on bit error rate (BER) degradations in detecting low-density parity-check coded multilevel phase-shift keying signals transmitted over a Rician fading channel. Based on the analytical system model which we previously developed using Monte Carlo simulations, we determine the BER degradations caused by the simultaneous influences of stochastic phase error, quadrature error, in-phase-quadrature mismatch, and the fading severity.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.449-451
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• 2008

This paper studies the instability between homopolar generator and constant power load with negative impedance characteristics, provides the design method of homopolar generator system which overcomes the instability. In case of magnitude and phase of impedance of source and load mismatch, control instability of source can occur. For the safety of phase of load impedance, the gain of P, I controller with sufficient phase margin is applied through analysis on the simulation model of generator system, and the gain limit of load impedance is ensured by limitation of the gain margin of generator system. The stability of power system can be increased by considering and analyzing the impedance of source and load.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.4
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• pp.41-47
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• 2004

In this paper, we analyze the microwave characteristics of traveling-wave electro-absorption modulator (TW-EAM) considering the microwave feedline and the impedance mismatch. The TW-EAM is analyzed by using the equivalent circuit model. The capacitance and the inductance of the equivalent circuit are evaluated by using 3-dimensional finite difference time domain (FDTD) method, while the microwave feedline is analyzed by momentum method. In a viewpoint of microwave characteristics, we present the effect of the structure and the length of microwave feedline.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.5
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• pp.319-326
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• 1988

In the presence of unmodeled dynamics, the robustness of adaptive pole assignment control using new pseudo-plant is presented. The pseudo-plant proposed by Donati et al. is modified as the gain of low pass filter can be set from zero to one. This modified pseudo-plant results in the reduction of modeling error. It is shown that not only this approach is insensitive to input frequency but also it improves the conic condition developed by Ortega et al. which is required to assure stability of adaptive control system despite the model-plant mismatch. A simple method to compensate the tracking error due to the use of pseudo-plant is considered.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.2
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• pp.67-72
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• 2005

This paper presents a method to select contingency ranking considering voltage security problems in power systems. Direct method which needs not the detailed knowledge of the post contingency voltage at each bus is used. Based on system operator's experience and knowledge, the membership functions for the MVAR mismatch and allowable voltage violation are justified describing linguistic representation with heuristic rules. Rule base is used for the computation of severity index for each contingency by fuzzy inference. Contingency ranking harmful to the system is formed by the index for security evaluation. Compared with 1P-1Q iteration, this algorithm using direct method and fuzzy inference shows higher computation speed and almost the same accuracy. The proposed method is applied to model system and KEPCO pratical system which consists of 311 buses and 609 lines to show its effectiveness.